Railroad rail assemblies use cross-ties to support the steel rails that carry freight and passenger trains. Historically the cross-ties have been made from wood, and have been treated with creosote. More recently, creosote has been classified as a carcinogen, and most localities have placed severe restrictions on its use, if not banned its use altogether. As a result, creosote-soaked cross-ties have been replaced with pressure treated timbers. Pressure treated timbers, however, have a substantially reduced life expectancy when compared to creosote timbers.
Another problem with wooden cross-ties is their inability to hold the rails they support within “Standard Gauge” for extended periods of time. Cross-ties must have some degree of flexibility in order to deflect under the load of a passing train, and to this extent wooden cross-ties exhibit sufficient support and durability. However, the inherent problem with any wooden tie is its limited useable life due to its tendency to decay when exposed to the elements. Consequently, degeneration of the wooden ties eventually loosens the railroad spikes, allowing the rails to move apart, which could eventually result in derailment. Therefore, the use of wooden cross-ties requires frequent maintenance and replacement. Also, the decay and breakdown of creosote soaked ties is a threat to the environment, in that State Statutes and Local Ordinances have drastically increased the cost associated with disposing of these types of cross-ties.
There have also been attempts to use reinforced concrete cross-ties and steel cross-ties to address some of the problems associated with wooden cross-ties. Concrete cross-ties, however, are expensive compared to wooden cross-ties and are not as flexible as wooden cross-ties. Concrete cross-ties have a tendency to fail under adverse conditions, at which time the cross-tie will need replacement. Accordingly, while concrete cross-ties can be used for “Light Rail” passenger track, they are not as suitable for freight tracks due to the extreme weights inherent in freight trains.
Steel cross-ties have also been used. While steel can handle the heavy weight of freight traffic and will last for long periods of time, steel cross-ties are also expensive compared to wooden cross-ties. In order to insure the integrity of steel cross-ties, frequent inspection and welding is required thus substantially increasing their maintenance costs.
Another known cross-tie is that of U.S. Pat. No. 5,996,901 to Young. The '901 cross-tie includes a stack of elastomeric layers (e.g., recycled tire treads) as a filler layer interposed between and fastened to a pair of rigid plates. The stack and plate assembly is held together by a plurality of wedge-shaped members and fasteners which are fixed to form non-perpendicular angles with the stack. The wedge-shaped members and bolts are positioned at multiple locations along the longitudinal (i.e., length) direction of the cross-tie.
Like the above-mentioned steel cross-ties, the '901 cross-tie assembly is expensive. The expense is attributed not only to the inclusion of the rigid plates (e.g., steel), but also to the high number of wedge-shaped members and bolts required by the design. Ultimately, the design of the '901 cross-time assembly is cost prohibitive.
It would be desirable to provide an environmentally friendly solution to the above-discussed problems with the prior art cross-ties. While several have attempted to provide such a solution, the expense involved has prevented any such solution from coming to fruition.